The invention relates to an air bag, and an air bag device, for protecting a driver at a time of a car collision. More specifically, the present invention relates to an air bag expanding to a space between the driver and a lower portion of a steering wheel, and an air bag device including the air bag.
An air bag device provided at a fixing portion in front of a seat in a vehicle is to protect a passenger or driver by quickly expanding an air bag with a pressure of a gas discharged from a gas generator called xe2x80x9cinflatorxe2x80x9d at an emergency situation, such as car collision.
In an air bag device for a driver, there may be provided a cloth for guiding a gas into the air bag for quickly expanding the air bag in an upper direction rather than a lateral direction when the inflator is actuated.
Incidentally, an xe2x80x9cupper direction of an air bag devicexe2x80x9d in the present specification is defined as an upper side or direction of the air bag in a posture of a steering system of the vehicle running straight where the air bag device is provided at a center of a steering wheel. Namely, the upper direction is a direction from the center of the air bag toward the front glass along the longitudinal direction of the vehicle. The same definition is applied to a lower, left and right directions.
Japanese Patent Publication (KOKAI) No. 10-226294 discloses an air bag wherein an inner bag is housed in an outer bag, and a gas is discharged in the upper and lower directions from gas flow-out ports provided at both upper and lower sides of the inner bag.
Japanese Patent Publication (KOKAI) No. 9-30353 discloses an air bag wherein two panel-shape straps are provided in parallel in the air bag and an inflator is disposed therebetween, so that a gas from the inflator is guided to the upper and lower directions in the bag by the straps.
In the air bag of Japanese Patent Publication No. 10-226294, a positional relationship between the gas flow-out ports of the inner bag and a steering wheel is not considered. In case the gas flow-out ports are retreated on a steering column side relative to the steering wheel, the gas flowing out from the gas flow-out ports is changed toward the driver by the steering wheel in its flowing direction. Therefore, the expanding speed in the upper and lower directions of the air bag does not become sufficiently large.
In the air bag of Japanese Patent Publication No. 9-30353, since the straps are employed instead of an inner bag, the gas from the inflator hits a front surface of the air bag, and is then branched to the upper direction and the lower direction of the air bag. Thus, the air bag does not sufficiently quickly expand in the upper and lower directions.
In view of the above defects, the present invention has been made and an object of the invention is to provide an air bag and air bag device, wherein the air bag is sufficiently quickly expanded especially in the lower direction.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to attain the above objects, an air bag according to a first aspect of the present invention includes an outer bag, an inner bag housed in the outer bag, an upper side flow-out port for allowing a gas to flow in an upper direction from the inner bag and a lower side flow-out port for allowing the gas to flow in a lower direction from the inner bag, wherein the upper side flow-out port and the lower side flow-out port are disposed on a driver""s side relative to a steering wheel plane in an expanded state of the inner bag.
According to a second aspect of the invention, an opening area of the lower side flow-out port may be made larger than that of the upper side flow-out port.
According to a third aspect of the invention, the lower side flow-out port may be disposed closer to an inner circumference of the outer bag than the upper side flow-out opening.
According to a fourth aspect of the invention, an air bag includes an outer bag and an inner bag having a gas flow-out port and housed in the outer bag, wherein the gas flow-out port of the inner bag allows gas to flow out only in a lower direction, and the gas flow-out port is disposed on a driver""s side relative to a steering wheel plane in an expanded state of the inner bag.
An air bag device according to the present invention includes the air bag, and a steering device according to the present invention includes the air bag device.
In the air bag, air bag device and steering device, in case a gas is ejected from an inflator, the gas is ejected to the upper and lower directions (or only lower direction) from the gas flow-out ports disposed on the driver""s side relative to the steering wheel plane. A flowing direction of the gas is hardly changed by the steering wheel, so that the air bag is quickly expanded in the upper and lower directions. In case an opening area of the lower side gas flow-out port is made larger than that of the upper side gas flow-out port of the inner bag, or only the lower side gas flow-out port is provided at the inner bag, the lower side of the air bag is expanded quicker than the upper side thereof.
In the present invention, it is preferable that the flow-out ports are positioned closer to the steering wheel side than a middle between the steering wheel plane and the farthest projected portion from the steering wheel surface of the air bag at a time of the largest expansion of the air bag.